For high data rate applications, the implementation of iterative turbo-like decoders requires the use of parallel architectures posing some collision-free constraints to the reading/writing process in the soft-input soft-output (SISO) decoders. Contrary to the literature belief, we prove in this paper that the parallelism constraints can be met by any permutation law employed by the turbo-interleaver, and we give a constructive method to satisfy those constraints.